In recent years, with the improvement of communication speed and the progress of cloud computing, the use of Near Field Communication (NFC) has been rapidly increasing. The NFC is commonly used for not only an IC card such as a cash card and a credit card, but also for electronic money stored in a smartphone and a smart card used as, for example, a ticket for train, bus, and the like. For the NFC, enhancement of security in an ID identification function for identifying an individual has been a problem. Furthermore, in recent years, an ID identification function is also incorporated in, for example, a memory card that has been used only to store individual data therein, and therefore, high-speed processing of the ID identification function in a portable device has become a technical problem. Under such circumstances, research and development for using variations among individual devices as “chip fingerprint” have been conducted. This technique is known as a Physically Unclonable Function (PUF).
Among PUFs, SRAM (Static Random Access Memory)-PUF is most widely studied recently. The SRAM-PUF is a technique using manufacturing variations between two inverters constituting an SRAM. In this technique, the RAM-PUF, which is the most widespread type of PUF, has been applied to devices such as security IPs and IC cards. Further, as a proposal to use initial variations among electronic devices, application of the RAM-PUF to a non-volatile memory is also under consideration.